Bug 833943 - Part 1: add a SessionMigration jsm to take care of migrating sessions, r=ttaubert

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extra : rebase_source : 68ae76fb342cd2e483c1d5f38a55ef1ce27235a1
Bug 833943, part 2: implement about:welcomeback, r=gavin
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Bug 833943 - Part 5: add about:welcomeback to gInitialPages

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rename : browser/components/sessionstore/content/aboutSessionRestore.xhtml => browser/components/migration/content/aboutWelcomeBack.xhtml
extra : rebase_source : fc58ab8f648c4e0298959429cbf52de40135bb3d
Bug 833943, part 3: implement migrator changes, r=MattN, sr=gavin

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extra : rebase_source : d94c1d1c84f9b996d92317a26cbd227c0cb97a44
Bug 887907 - Move OS.File to use Promise.jsm; r=gps

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extra : rebase_source : cab194eea7781dfd5c14732a77710d6d7904525b
Bug 887814 - Don't use mp-clang in MacPorts bootstrapper; r=BenWa

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extra : rebase_source : 1513b7f62d62e5250a9382d0ac8ba1f3df8890ab
Bug 884587 - Part 0: Teach FileCopier how to remove unwritable files on Windows; r=glandium

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extra : rebase_source : 2a340802af58159adaf2c11b0928e237c746f699
Bug 884587 - Part 1: Perform file removal with purge manifests; r=glandium

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extra : rebase_source : bfe9c0eb27d5b19e26e557af8762bb45c21b949e
Bug 884587 - Part 2: Add EXPORTS files to purge manifest; r=glandium

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extra : rebase_source : 5b783b192d0324ef7b867a8229d2e5f55d482aac